Microcomputer chip with function capable of supporting emulation

ABSTRACT

A microcomputer chip includes a plurality of first electrode pads arranged in a chip circumferential section; a plurality of second electrode pads arranged inside from the plurality of first electrode pads; and an emulation circuit connected with the plurality of second electrode pads to interface with an external unit in emulation. The plurality of second electrode pads may be arranged on an area where a functional circuit is formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a microcomputer. Morespecifically, the present invention is directed to a microcomputer chipinto which a function capable of supporting emulation has beenassembled, a semiconductor device on which the above-explainedmicrocomputer chip has been mounted, and an emulator for performingemulation of this microcomputer chip.

2. Description of the Related Art

In a microcomputer (to be referred to as “single chip microcomputer”hereinafter) which mounts thereon a program storing-purpose memory as aROM, a software program to be installed in the single chip microcomputerneeds to be developed. In order to develop and debug the above-describedsoftware program, an “emulator” has been conventionally used. Theemulator emulates a function of the microprocessors, and provides anenvironment for debugging the operation of the software program andconfirmations of the operation of a hardware circuit. For this purpose,the emulator is provided with a chip for emulating the function of aproduct, and an “evaluation chip” for controlling the chip. As theemulator, for example, “ICE (In-Circuit Emulator: registered trademark)”is known. Also, an operation for developing and debugging a softwareprogram by use of an emulator is referred to as “emulation.”

When an emulator is constructed, a chip for emulating the functions of aproduct chip is necessary. However, it is not desired to develop thisemulation chip separately from the product chip, in view of acost-to-effect aspect. For this reason, it is proposed to incorporatethe function for supporting the emulation in the product chip. In thiscase, since this supporting function is no longer required at a time ofshipping the product chip, it is desired to suppress increase of a chiparea through adding this supporting function.

As general-purpose techniques capable of suppressing the increase of thechip area, the following techniques are known.

That is, Japanese Patent Laid Open Patent Application (JP-A-Heisei3-173433: a first conventional example) discloses a semiconductorintegrated circuit device in which pads are arranged at a peripheralportion of a chip, and are electrically connected to external terminals.In this semiconductor integrated circuit device, these pads are arrangedin two or more lines along the edges of this chip. Further, at least twolayers are formed in a thickness direction of the chip to constituteinternal wiring lines for electrically connecting the pads to aninternal circuit. Also, in this conventional example, the pads otherthan the pads in the outermost line are used as test terminals, whichare used to test LSI functions in a wafer stage. For this reason, thebonding wire is not connected to the test terminal. Only the pads in theoutermost line are electrically connected to the external terminals.

Also, Japanese Laid Open Patent Application (JP-P2002-299567A: secondconventional example) discloses a semiconductor device in whichelectrode pads are arranged and formed on a partial structural elementof an integrated circuit formed on a semiconductor wafer. This structureis referred to as a “CUP (Circuit Under Pad).”

A microcomputer into which a function for supporting emulation isincorporated is packaged and then is connected to an emulator. In otherwords, the microcomputer contains a circuit interfacing with theemulator at least. Electrode pads used to connect this circuit with theexternal emulator are referred to as “emulation pads.” On the otherhand, electrode pads for normal use are referred to as “product pads.”

In order to suppress increase of a chip area, it could be consideredthat that product pads are commonly used as emulation pads. The commonpads are connected to switch circuits, which control the common pads tobe connected to the normal circuit and the emulation circuit in responseto control signals. For instance, it is assumed that a microcomputerchip has a first pad connected to the switch circuit. In this case, thefirst pad is connected to the emulation circuit when a software programis developed. For this reason, a function of a port connected to thefirst pad in the normal operation cannot be confirmed. Therefore, inorder to confirm this function, another microcomputer chip having asecond pad different from the first pad and connected to a switchcircuit must be prepared separately from the microcomputer chip. In thisway, although increase of the chip area can be avoided if the electrodepads are commonly used to the emulation pads, sorts of chips to beprepared are increased.

SUMMARY OF THE INVENTION

In an aspect of the present invention, a microcomputer chip includes aplurality of first electrode pads arranged in a chip circumferentialsection; a plurality of second electrode pads arranged inside from theplurality of first electrode pads; and an emulation circuit connectedwith the plurality of second electrode pads to interface with anexternal unit in emulation.

Here, the plurality of second electrode pads may be arranged on an areawhere a functional circuit is formed.

The plurality of second electrode pads may be arranged along a part ofthe plurality of first electrode pads. In this case, the plurality ofsecond electrode pads may be arranged according to one of sides of themicrocomputer chip. Otherwise, the plurality of first electrode pads andthe plurality of second electrode pads may be arranged in a zigzagmanner.

In another aspect of the present invention, a microcomputer chipincludes a plurality of first electrode pads arranged in a chipcircumferential section; and a plurality of second electrode pads towhich wire bonding is carried out for emulation.

Here, the plurality of second electrode pads may be arranged on an areawhere a functional circuit is formed.

Also, the plurality of second electrode pads may be arranged along apart of the plurality of first electrode pads. In this case, theplurality of second electrode pads may be arranged according to one ofsides of the microcomputer chip. Otherwise, the plurality of firstelectrode pads and the plurality of second electrode pads may bearranged in a zigzag manner.

In another aspect of the present invention, a microcomputer deviceincludes a memory in which a software program is stored; a peripheralcircuit; an input/output circuit; a CPU configured to execute thesoftware program to control the peripheral circuit and the input/outputcircuit; a plurality of first electrode pads arranged in a chipcircumferential section and connected with the input/output circuit; aplurality of second electrode pads arranged inside from the plurality offirst electrode pads; and an emulation circuit connected with theplurality of second electrode pads.

Here, the plurality of second electrode pads may be wire-bonded to anexternal unit for emulation.

In another aspect of the present invention, an emulator system includesa microcomputer device; and a control device connected with themicrocomputer device. The microcomputer device includes a memory tostore a software program; a peripheral circuit; an input/output circuit;a CPU configured to execute the software program to control theperipheral circuit and the input/output circuit; a plurality of firstelectrode pads arranged in a chip circumferential section and connectedwith the input/output circuit; a plurality of second electrode padsarranged inside from the plurality of first electrode pads; and anemulation circuit connected with the plurality of second electrode pads.The control device is connected with the microcomputer device throughthe plurality of second electrode pads and controls the peripheralcircuit through the emulation circuit and the plurality of secondelectrode pads in emulation.

In another aspect of the present invention, a method of developing amicrocomputer, may be achieved by (a) providing a microcomputer chip foremulation which may include: a plurality of first electrode padsarranged in a chip circumferential section, a plurality of secondelectrode pads arranged inside from the plurality of first electrodepads, and an emulation circuit connected with the plurality of secondelectrode pads to interface with an external unit; by (b) producing adevelopment-purpose package by wire-bonding the plurality of firstelectrode pads and the plurality of second electrode pads with theexternal unit; by (c) developing a software program to be loaded into amicrocomputer through emulation using the development-purpose package;by (d) writing the developed software program in a memory area in amicrocomputer chip for a product, the microcomputer chip for the producthaving a same configuration as that of the microcomputer chip for theemulation; and by (e) carrying out wire-bonding to the plurality offirst electrode pads without carrying out wire-bonding the plurality ofsecond electrode pads to produce a product-purpose microcomputer chip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing a configuration of amicrocomputer according to the present invention;

FIG. 2 is a plan view showing the microcomputer chip according to afirst embodiment of the present invention;

FIG. 3 is a cross sectional view showing a structure of themicrocomputer chip taken along a line A-A′ shown in FIG. 2;

FIG. 4 is a conceptional diagram showing a configuration of amicrocomputer developing system according to the first embodiment of thepresent invention;

FIG. 5 is a flow chart showing a microcomputer developing methodaccording to the first embodiment of the present invention;

FIG. 6 is a plan view showing the microcomputer chip according to asecond embodiment of the present invention; and

FIG. 7 is another plan view showing the microcomputer chip according tothe second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a semiconductor device incorporating a microcomputer of thepresent invention will be described with reference to the attacheddrawings.

FIG. 1 is a block diagram showing a configuration of a microcomputer 1according to the present invention. This microcomputer 1 is providedwith a CPU (Central Processing Unit) 3, a ROM (Read-Only Memory) 4, aperipheral circuit 5, an input/output circuit 6, and an emulationcircuit 7, which are all connected to a bus 2. The input/output circuit6 operates as interface ports with an external unit. A software programfor a function of this microcomputer 1 is stored in the ROM 4. When themicrocomputer 1 is used for the product, the CPU 3 reads out thesoftware program stored in the ROM 4, and then executes the program.Thus, the function can be realized by the CPU 3.

When the microcomputer 1 is developed, development of a software programto be stored in this ROM 4 is carried out. In order to develop thissoftware program, an “emulator” is used to provide an environment for adebugging operation of the software program and operation confirmationof a hardware circuit. When the emulation is carried out, the emulatoris connected to the emulation circuit 7 of the microcomputer 1. In otherwords, the emulation circuit 7 contains an I/O buffer at least, andprovides a function of interfacing with an external unit (not shown) onthe emulation. Instead of the CPU 3 and the ROM 4, instructions areissued via the emulation circuit 7 to the peripheral circuit 5, andstatuses of the peripheral circuit 5 are monitored through thisemulation circuit 7. Thus, the debugging operation of the softwareprogram and the operation of the hardware circuit are confirmed.

In this way, the function of supporting the emulation is incorporated inthe microcomputer 1 according to the present invention. As aconsequence, this microcomputer 1 may not only be shipped as theproduct, but also may be used in emulation. An emulation environment maybe built up by the microcomputer 1 according to the present inventionand the emulator.

First Embodiment

FIG. 2 is a plan view showing a microcomputer chip 10 according to thefirst embodiment of the present invention. This microcomputer chip 10 isprovided with a plurality of first electrode pads 11, and a plurality ofsecond electrode pads 12.

The plurality of first electrode pads 11 are connected to input/outputports of the input/output circuit 6 and are used as input/output pads ofdata signals for the emulation as well as the input/output pads for thenormal use. As shown in FIG. 2, the plurality of first electrodes 11 arearranged in a single line along four edges of the microcomputer chip 10.In other words, thee plurality of first electrode pads 11 are arrangedin the single line in a circumferential portion of the microcomputerchip 10. The plurality of first electrode pads 11 are wire-bonded toleads (not shown) provided outside the microcomputer chip 10 andconnected to an external unit. In view of a bonding process, it ispreferable that the plurality of first electrode pads 11 are arranged inthe chip circumferential portion in a same interval. As a total numberof these first electrode pads 11 is 64, for example (some of the firstelectrodes are omitted in FIG. 2).

The plurality of second electrode pads 12 are connected to the emulationcircuit 7 and are exclusively used as emulation pads for the emulation.The plurality of second electrode pads 12 are wire-bonded with externalwiring lines (not shown) only for the emulation, through which anexternal controller is connected. As shown in FIG. 2, the plurality ofsecond electrode pads 12 are arranged partially on the inner side fromthe plurality of first electrode pads 11. Thus, it is possible to avoidthat the second electrodes 12 hinder the bonding process of the firstelectrodes 11. A total number of the second electrode pads 12 may be aminimum and necessary number. For instance, the total number is in arange of 10 to 20. As shown in FIG. 2, the plurality of second electrodepads 12 are arranged in some groups along a portion of the plurality offirst electrode pads 11.

As described above, according to the microcomputer chip 10 of the firstembodiment of the present invention, the second electrodes 12 which arededicated to the emulation are provided. Since the product pads (namely,first electrode pads 11) need not be used as the emulation pads, two ormore sorts of chips are no longer prepared when a microcomputer isdeveloped. In other words, according to this microcomputer chip 10, thedeveloping cost thereof can be reduced while eliminating the uselessmicrocomputer chip. Also, since the product pads need not be used as theemulation pads, it is possible to avoid the performance of themicrocomputer 1 is lowered.

Furthermore, in accordance with the microcomputer chip 10 of the firstembodiment of the present invention, the second electrode pads 12 whichare exclusively used for the emulation are arranged inside the firstelectrode pads 11. The second electrode pads 12 are not additionallyprovided on the line along which the first electrode pads 11 arearranged, so that increase of the area for this microcomputer chip 10can be suppressed. Also, an arrangement of the plurality of secondelectrode pads 12 never gives an adverse influence to the arrangement ofthe plurality of first electrode pads 11. As a consequence, when aproduct is manufactured, the plurality of second electrode pads 12 neverhinder wiring of the plurality of first electrode pads 11. Since themicrocomputer chip 10 according to the first embodiment of the presentinvention may be used as a product, the structure is suitable.

Alternatively, as shown in FIG. 2, both of the first electrode pads 11and the second electrode pads 12 may be arranged in a zigzag shape. Thatis to say, each of the plurality of second electrode pads 12 may bearranged between adjacent two of the first electrode pads 11. As aconsequence, the internal wiring lines which are connected to both ofthe first electrode pads 11 and the second electrode pads 12 can bearranged in a higher efficiency within the microcomputer chip 10.Accordingly, the entire area of this microcomputer chip 10 can bereduced.

FIG. 3 is a cross sectional view showing the structure of themicrocomputer chip 10, taken along a line A-A′ shown in FIG. 2. As shownin FIG. 3, for instance, an input/output buffer 22 is formed on a wafer21 of this microcomputer chip 10. A predetermined wiring line 24 isformed via an interlayer insulating film 23 on the input/output buffer22. A second electrode pad 12 and the input/output buffer 22 areelectrically connected to each other via the wiring line 24 and avia-contact 25.

In this structure, the plurality of second electrode pads 12 arearranged above a region where a function circuit has been formed. Forinstance, as shown in FIG. 3, the second electrode pads 12 are formedabove the input/output buffer 22. In other words, this microcomputerchip 10 has a CUP (Circuit Under Pad) structure. As a result, the chiparea of the microcomputer chip 10 may be furthermore reduced. It shouldbe understood that similar to the second electrode pads 12, the firstelectrode pads 11 may be formed on the integrated circuit region. Inthis case, the area of the microcomputer 10 may be further reduced.

FIG. 4 is a conceptional diagram showing the configuration of amicrocomputer developing system 100 according to the first embodiment ofthe present invention. The microcomputer developing system 100 containsan emulator 50 and a terminal unit (PC: personal computer) 60. Theemulator 50 provides an environment that a debugging operation of asoftware program is carried out and an operation of a hardware circuitis confirmed. More specifically, the emulator 50 is provided with a“product board” 31, a “common board” 41, and the like. The “productboard” 31 is used to mount thereon the microcomputer chip 10 which isdeveloped. The “common board” 41 is used to mount thereon an evaluationchip 40 which provides common functions (replacement of CPU/ROM, statusmonitor etc.) which are required in emulation. Since the product board31 and the common board 41 are used, an emulation environment may beconstructed. It should also be understood that the product board 31 maybe replaced by another product board (not shown). Also, a user system(not shown) is connected through a cable to the product board 31.

The terminal unit 60 is connectable with the emulator 50, and provides auser interface. Into this terminal unit 60, development supportingsoftware 70 for a software program to be distributed is installed. Auser executes the development supporting software 70, and can issuevarious sorts of instructions to the emulator 50, while the user refersto information displayed on a display unit of the terminal unit 60. Theemulator 50 executes emulation in response to the instruction issuedfrom the user.

When software program is developed, the plurality of first electrodepads 11 and the plurality of second electrode pads 12 of themicrocomputer chip 10 according to the first embodiment of the presentinvention are bonded with leads (namely, external wiring lines).Thereafter, the electrode pads 11 and 12 are processed via a resinsealing step, so that a package 30 is obtained. As the package 30obtained at this time, a BGA (Ball Grid Array) is exemplified. Since afreedom degree of a substrate which mounts thereon the chip 10 isrelatively high, this BGA package can be readily bonded with both of thefirst electrode pads 11 and the second electrode pads 12. The package 30which has been formed in the above-described manner is mounted on theabove-described product board 31.

The plurality of second electrode pads 12 of the microcomputer chip 10contained in the package 30 are connected to the evaluation chip(control device) 40 mounted on the common board 41. In other words, theemulation circuit 7 of the microcomputer chip 10 which is to bedeveloped is connected via predetermined wiring lines to the evaluationchip 40. The evaluation chip 40 outputs various sorts of instructions inresponse to a command issued from the user. The outputted instructionsare directly supplied via the plurality of second electrode pads 12 andthe emulation circuit 7 to the peripheral circuit 5. In this case, atotal number of the plurality of second electrode pads 12 is equal to,for example, 10. The instructions outputted from the evaluation chip 40are supplied in a parallel. In this way, the evaluation chip 40 controlsthe emulation. The user can develop the software program in a highefficiency by using this emulator 50.

After the software program is developed, a package functioning as aproduct is manufactured. As this product, the same microcomputer chip 10is used. However, when the product is manufactured, only the pluralityof first electrode pads 11 are wire-bonded with the leads (externalwiring lines). Thereafter, the first electrode pads 11 are processed viaa resin sealing step, so that a package used for the product ismanufactured. As this package obtained at this time, a QFP (Quad FlatPackage) is exemplified. As described above, although the microcomputerchip 10 used when the software program is developed and themicrocomputer chip 10 when the product is manufactured have a samecircuit configuration and circuit pattern, the resulting packages may bedifferent from each other.

FIG. 5 is a flow chart showing a developing method of a microcomputeraccording to the first embodiment of the present invention. In this flowchart, in a first step S1, the microcomputer chip 10 shown in FIG. 2 isprovided. Next, a developing operation of a software program to bestored in the ROM 4 is carried out. For this purpose, a package for adevelopment purpose, for example, a BGA type package is used. In thisstep S2, both of the first electrode pads 11 and the second electrodepads 12 are bonded with the external wiring lines. Next, while thisdeveloping-purpose package 30 (namely, BGA type package) and themicrocomputer developing system 100 shown in FIG. 4 are utilized,emulation is carried out. Thus, the software program may be developed ina step S3.

Subsequently, a product is manufactured. More specifically, themicrocomputer chip 10 having the same circuit configuration is provided,and the software program which has been developed in the previous stepis written into a storage region of the ROM 4 in a step S4. Next, apackage for a product is formed. For instance, a QFP type package isused. Also, in this case, only the first electrode pads 11 arewire-bonded to the external wiring lines in a step S5. As a result, theproduct may be accomplished in the above-explained manner (step S6).

Second Embodiments

In FIG. 2, the plurality of second electrode pads 12 are arranged alongthe four sides of the microcomputer chip 10. However, the presentinvention is not limited only to this arrangement of the plurality ofsecond electrode pads 12.

FIG. 6 is a plan view showing one example of the microcomputer chip 10according to the second embodiment of the present invention. Similar tothe first embodiment, the plurality of second electrode pads 12 arearranged inside the plurality of first electrode pads 11. In this secondembodiment, the plurality of second electrode pads 12 are notdistributed, but are arranged at a predetermined region in aconcentration manner. As a consequence, structural elements of theemulation circuit 7, which are connected to the plurality of secondelectrode pads 12 may be easily concentrated to one place. Thus, it ispossible to avoid that the emulation circuit 7 which is used only whenemulation is carried out reduces the chip area of a main circuit. As aresult, increasing of an area of this microcomputer chip 10 may besuppressed.

FIG. 7 is a plan view showing another example of the microcomputer chip10 according to the second embodiment of the present invention. Similarto the first embodiment, a plurality of second electrode pads 12 arearranged inside the plurality of first electrode pads 11. Also, similarto the case shown in FIG. 6, the plurality of second electrode pads 12are arranged at a predetermined area in a concentration manner.Furthermore, in this example, the plurality of second electrode pads 12are arranged in one direction along one side of the microcomputer chip10. Effects achieved by the above-described example are given asfollows:

That is, as described above, when the emulation-purpose package 30 ismanufactured, both of the first electrode pads 11 and the secondelectrode pads 12 are wire-bonded to the leads. As a consequence, incase of wire bonding, wires which are bonded to the first electrode pads11 are easily contacted to wires which are bonded to the secondelectrode pads 12. More specifically, when a resin sealing step isexecuted, the bonding wires are flextured by the resin to be injected,so that the flextured bonding wires may be readily contacted to theadjoining bonding wire. In accordance with this example, the pluralityof second electrode pads 12 are arranged along one direction. As aresult, if the injection direction of the resin is adjusted, the bondingwires are not featured. Thus, the contact of the bonding wires can beprevented and generation of shirt-circuit can be prevented.

It should also be noted that both of the first electrode pads 11 and thesecond electrode pads 12 may be preferably arranged in the zigzag formalso in this second embodiment. Further, it is preferable that themicrocomputer chip 10 owns the CUP structure shown in FIG. 3. As aresult, increasing of the area of this microcomputer chip 10 can besuppressed.

As previously described, in accordance with the present invention, thedeveloping cost for the microcomputer can be reduced. Also, it ispossible to avoid that the performance of the microcomputer is lowered.Furthermore, increasing of the chip area can be suppressed.

In accordance with the microcomputer chip, the semiconductor device, andthe emulator of the present invention, total cost required fordeveloping a microcomputer can be reduced. Also, in accordance with themicrocomputer chip and the semiconductor device of the presentinvention, it is possible to avoid that the performance of themicrocomputer is lowered. Also, in accordance with the microcomputerchip and the semiconductor device of the present invention, increasingof the area of the microcomputer chip can be suppressed. Further, inaccordance of the microcomputer chip and the semiconductor device of thepresent invention, it is possible to avoid that bonding wires are madecontact to each other.

1. A microcomputer chip comprising: a plurality of first electrode padsarranged in a chip circumferential section; a plurality of secondelectrode pads arranged inside from said plurality of first electrodepads; and an emulation circuit connected with said plurality of secondelectrode pads to interface with an external unit in emulation.
 2. Themicrocomputer chip according to claim 1, wherein said plurality ofsecond electrode pads are arranged on an area where a functional circuitis formed.
 3. The microcomputer chip according to claim 1, wherein saidplurality of second electrode pads are arranged along a part of saidplurality of first electrode pads.
 4. The microcomputer chip accordingto claim 3, wherein said plurality of second electrode pads are arrangedaccording to one of sides of said microcomputer chip.
 5. Themicrocomputer chip according to claim 3, wherein said plurality of firstelectrode pads and said plurality of second electrode pads are arrangedin a zigzag manner.